Overload cutout for electric circuits



Aug. 10, 1943. J, F. FRESE OVERLOAD CUTOUT FOR ELECTRIC CIRCUITS Filed Feb. 2, 1942 3 Sheets-Sheet l Aug. 10, 1943. J, FRESE 2,326,529

OVERLOAD CUTOUT FOR ELECTRIC CIRCUITS Filed Feb. 2, 1942 3 Sheets-Sheet 2 Aug. 10, 1943. J. F. FRESE 2,326,529

OVERLOAD CUTOUT FOR ELECTRIC CIRCUITS Filed Feb. 2, 1942 3 Sheets-Sheet 3 tached switch member,

Patented Aug. 10, 1943 ENT OFFICE j Y'OVERLOAD OUTOUT'FOR ELECTRIC 1 CIRCUITS Joseph Frese, Baltimore, Md., assignor to Monito'r Controller Company, Baltimore, Md., a corporation of Maryland Application February 2, 1942', Serial No. 429,334

3 Claims.

This invention relates to a thermally-responsive overload cut out for electric circuits, particularly adapted; for protecting elec'tricmotors from injury by excessive current in the armature circuit of the moton'due to overload. The invention comprises an-overload coiladaptedto be connected inseries with the armature of a motor and two thermally responsive coils, one affected by the temperature in the overload coil,

for causing the operation" of a switch, and the other affected only by atmospheric temperature and adapted 'to compensate for changes inatmospheric temperature so that the operation of Figure 4 is a vertical section on the line l4 of Figure 3; a

Figure 5 is asectioiion the line 5-5 of Figureyl;

Figure 5 is a plan viewof the arm which connects the lower end ofthelower thermally responsive coil pivotally to the spindle and serves as a device for retaining and releasing the latch;

Figure'6 is, a section on the line 66 of Figure 3;

Figure '7 isa side view of the device, partly in section,- showing the lever ,and switch in tripped positions;

' Figure 8 is a similar view illustrating the operation of resetting the lever and switch;

Figure 9 is a perspective view of the lever and switch; a g I Figure 10 is an elevationof the lever and at- -looking from right to leftin Figure 9;

Figure 11 is a central verticalsection through partsof the upperand lower .bi-metallic coils, the guide ring which surrounds the lower part of the upper coil, and the insulating coupling which joins the spindle parts;

Figure 12 is a section on the line, l2 l2 of Figure 3; r

Figure 13 is a detail perspective view of the switch lever, and i Figure'14 is a section on the line I4-|4 of Figure '10. .1

In the drawing Aindicates a frame of insulating materiaL-such as hard rubber, comprising a base I, a top piece. 2 and parallel upright parts 3 and 4, spaced apart and connecting the top and bottom pieces near their ends. U-shaped metal clips 5 and 6, spaced apart, are secured to oneend of the top piece and constitute terminals to which wires forming part of the armature circuit of an electric motor may be'attached and to which the terminals of a wire coil 1) are attached so that it will be included in the armature circuit. The coil b, which heats when the motor is overloaded is vertically arranged above the central portion of the top piece and has its terminals secured to flat pieces of metal 5 and 6 whichrest upon the clips 5 and 6, respectively, and are secured thereto by screws 1 which extend through the clips and the top piece of the frame. As shown in Figures 1 and 2, the lower end of the overload coil b is secured to the metal part 6 while the upper end of the coil is secured to a metal post 5 extending upward from the part 5. By these connections the coil is held securely with its axis extending vertical- 1y. i 1 l Within the overload coil b and concentric with it, although not in Contact with it, is a bi-metallic thermally responsive coil 0' the upper end of which is turned radially inward andv secured within a slot in theupper end of a spindle D the lower end of which is journalled in a socket 8 in the base piece of the frame. The spindle D is composed of two metal rods d and d, rigidly connected together by a coupling d of insulating material, such as hard rubber, so that the several parts of the spindle turn as a unit. The top piece of the frame has a central opening 9 through which the spindle extends and into which the lower end of the coil 0 extends. This openingypartly circular in form, has a'lateral recess 9. The lowermost convolution of the coil 0 has its end portion 10 bent radially outward and this end portion extends into the recess 9* between two pointed adjusting screws I l and I2, as shown in Figure 6. A ring 12 is arranged upon the part 2 of the frame, to guide and center the lower end of the coil 0. This ring is held in place upon the part 2 of the frame by screws 0 the heads of which project over the edge of the ring. These screws hold the ring in place on the top piece, but do not prevent a limited-circumferential adjustment of the ring. The ring has a projection n which extends over the lateral recess 9 in the frame and the end portion n of this projecting part is bent downwardly'and welded to the end portion H) of the coil 0. The welded ends of the coil and ring extend between D while'its lower end is held against rotation, any

The lever has, secured to the sideopposite that to which the latch is secured,a U-shaped switch- 'member J, shown best in Figure9, made of V thin resilient metal, the arms 9' of this member being secured at their lower ends to the lever by rivets r, and to the upper central part of the member is secured a contact strip [5 adapted to engage and electrically connect st'ationary contacts on terminals l7 and I8"for the circuitwhich expansion or contraction of the coil 0 causedby changing temperature in' the surrounding overjload coil b, will cause an adjustment of the spin-- d1e D. To ofiset' the'effect of atmospheric temperature on the expansi'onand contraction of the coil 'c a compensating iii-metallic coil' cis arranged about the lower half d of the spindle.

is to be controlled, these terminals being secured to the top piece of the fram atthe end of the 'top piece opposite to that 0n'which the terminals 5- and'B are mounted.

While the circuits are not shown; it will be understood that in operation the overload coil 1) v will be connected in the motor circuit and a relay magnet used to control the opening and closing This latter coil has its upper end secured 'to' the coupling d while its lower end is connected to the side of a small metal arm I3 which is jou'r-' -:nalled on -'the part dcf" the spindle and has at ozone.'sideian-upturned' flange li to which the -lowerendof theicoil 'ciis secured. The outer .:end t3 'of this arm iscurved concentrically with rfthe'iaxis of the spindlega'sshownin Figures 5 ---and=-5 The coils c and'c are wound in the same direccofthe motor circuit, will have its coil connected in thecircuit which includes the terminals l land I 8 so'that while the motor may operate when the relay circuitis 'closedaat these terminals it will stop "when therela'y-circuit is opened. Figures .1

- and 3 .show the parts: innormal ru'nningpcsition :tion. Asthe'coil c is'anchored at its lower end and secured at its upper-end to 'the spindle; when this coil expands'or contractsit turns-the spindle a's' an Jentirety, including the coupling 01 the movement being clockwise; as viewed from above,

when the 'coilexpands. 5A the upper end of the :lower coilc' is secured to the coupling this coil and Figure 7.showsth'e positions ofthe'fparts after the 'switchcontrolling the relay circuit has been opened: by reasonof overload in the armaturecircuit of the motor.

A vertically'mova-ble marten- 0% insulating material,isaarranged in thevertical slotZ, in the.

partdof the frame; and this rod extends through aslotinthe toppiece- 2 and has a knob EZat-its upper end. A spring 23;.between'the knob and willbe moved by the' spindle,.-but asvthe'coil'c .is-affected by "atmospherictemperature only it will contract in cold weather and adjustthe arm I-'3 clockwise onthe spind1e,whileinrhot weather this'adjustment willjta' ke'place in the counter iw'clock-wise direction, assuming the"therma1ly :re-

' sponsive O0l'1S.'t0 .be wound and connected as shown and described. The position of the arm I3 will therefore always be that to which it would be a'djusted by-the coil 0 if affected only byheat Zfronr'the overloadcoil.

A' switch lever E, comprising parallel side pieces -.e, connected by 'a cross piece e and having parallel supporting arms "e 'projecting at a right angleffrom the side pieces; is pivotally mounted \upona-pivot-pin e 'which extends through per-- ffo'ration in the armsand a perforation in thepart ltOf lZhG-fltlilG. Secured centrallytotthe cross .piece'e" isan arm'e by'which the fram may be rocked about its pivotal axis, as hereinafter derscribed.

A 'spring'latch H, adapte'd'to engage the arm' its, is secured to one sideof the lever. This latch,

. which is made of thin resilient sheet metal, comthe top piece normall fholdsctherod in an upper 7 position. The rod hasprojecting'from oneedge a shoulder 24 which normally engages a stop. pin

25 to limit the upward movement of the rod. v

To start'the motor therod is pushed downward. Duringthe first part of its downward movement a cam surface 24% on the shoulder engage the contact piece l Grand moves it to open position as shown in Figure.& thereby opening the controlled circuit. Further downwardmovement of the a rod causes its lower-end to engage the arm e on the leverand rock itso that the-latch willengage the end of the; arm v l3 and be fric- H tionally retained thereby, as shown in Figure 8.

The "knob 22 is then released and, as the rod K .movesupward'the cam on the rodreleases the contact piece lfi and'the latterm'oves to close the ,controlled circuit.- l

e {The foregoing statement offoperation is onthe positionlto be engaged bythe latch, but if, by

assumption that the arm 13 on the'spindle is in "reason of overload, ithe arm I3 has been; moved out of its normal position, the'nf -upo'n' depressing ,-therod Kthe latchwillnot'be retained infthe iprises two'parallelarmshriveted at their-upper j endsto the lever asvs'ho'wn. at s and'having a foot '-h ;projecting approximatelyat a right angle to 's'aid arms; this footphaving a 'slot l4 :through which the lowerpart d'iofJthe spindle eXtends, thisfoot tapering asshown in Figures 5 'and'9 and having a short-upturned flange 15 at itsend ladapted'tocfrictionallyengage the curved surface --of thearm t3 Qn-the'sp'indle, as shown inFigures '1, 13 and 8. The lower'ends'e of the leverarms are of reduced width and extend loosely through .holes-h? inthe foot of the latch so that the'lever may move the; foot positively from the unlatched position shown in'Figure 7 to the positionwhere .the part I5 on the latch may spring upwardly into frictional engagement-withv the curved endof the a .sh wi n F res. 3 land. 8-: 1

positionshown in' Figure 8 an'd,upon release of the rod, the leverglatch'and' contact member l6 'Will return to the positions shown in Figure?" and the controlled circuit will not be'closed. If, howr every thearm 13 is in its normal' position} when the rod K'is depressed; said a-rrnw illlbe engaged,

by "the latch-and the latch and lever ;will' e held in the positions shown inf'Figu're 1' after the, rod

is released. Asthe s'houlde r il i moves teits uppermost position, out of engagement with the contact. member f6, the latter will move into eng'agement with the contacts on the terminals 1'! and l3.of the controlled circuit, closing' the latter.

While the motor is running without overload,

the arm l3 will-beengagedbythe latch-,but, if

overloaded, the' arm I 3 willbe moved clockwise from the POSilIi'OIISfShOWIl:iniFlgllreS lial'Id 5,: out

i of engagement with ithe :flange 55 on qthe latch,

and the latch, lever and contact member I6 will then move to the positions shown in Figure 7.

In order to give the lever, latch and switch contact member It a positive and quick movement from the positions shown in Figure 1 to the positions shown in Figure '7, I provide a fiat springinetal strip F, which lies against one of the arms 9 of the switch member J and is secured at its lower end to the lever and switch member by one of the rivets 1'. Attached to the upper end of the spring F is an arm I which, as the lever is brought to switch closing position, bears against the part 4 of the frame. As the spring is attached to the lever below the axis of the latter and the part I engages the part 4 of the frame above the axis of the lever, the lever and the attached switch member will be spring-pressed in the direction to cause a quick movement of the parts from the position in Figures 1 and 8 to that shown in Figure 7 when the latch is released from the part l3 by reason of overload in the motor circuit.

What I claim is:

1. An overload cutout device for electric circuits comprising a suitable supporting frame, an overload coil mounted on the frame, a spindle extending axially through and beyond said coil, two thermally responsive coils surrounding said spindle, one of the latter coils being within the overload coil and having one end secured to the frame and its other end secured to the spindle, and the other thermally responsive coil being external to the overload coil and having one end secured to the spindle and its other end free to turn, a tripping device journalled on the spindle and connected to the free end of the last mentioned coil, a switch, comprising a lever and contact member, and a latch carried by said lever and adapted to engage and be held by said triping device while the spindle is in normal position and to be released when the spindle is moved in response to heating caused by excess current in the overload coil.

2. An overload cut out for electric circuits comprising a suitable supporting frame, an overload coil mounted on the frame with its axis extending vertically, a spindle extending axially through and below said coil, said spindle composed of two metal rods joined end to end by a coupling of insulating material, two thermally responsive coils, wound in the same direction, surrounding said spindle, one of the latter coils being within the overload coil and having its lower end adjustably secured to the frame and its upper end attached to the spindle, and the other thermally responsive coil having its upper end secured to the coupling and its lower end free to turn, a tripping device movable by said lower end, and a switch adapted to be held in closed position by said tripping device when the latter is in normal position and to be released therefrom when said device is moved from normal position in response to heating caused by excess current in the overload coil.

3. An overload cut-out device for electric circuits comprising a suitable supporting frame, an overload coil mounted thereon, a spindle extending axially through and beyond said coil, two bimetallic thermally responsive coils, wound in the same direction, surrounding said spindle, one of the bi-metallic coils being arranged within the overload coil and having one end secured to the frame and its other end secured to the spindle, and the other bi-metallic coil being without the overload coil and having one end secured to the spindle and its other end free to turn, a tripping device connected to the free end of the last mentioned coil, a switch comprising a lever and a switch member spring-pressed toward open posit-ion, a latch, carried by said lever, adapted to engage said tripping device when the lever and switch member are moved toward switch-closing position, and means for moving the lever and latch to the latching position and then permitting the switch to close, if the latch engages and is held by said tripping device.

JOSEPH F. FRESE. 

